SQL Group By

















Home
SQL Basics:

SQL HOME
SQL Introduction
SQL Select
SQL Where
SQL And & Or
SQL Between
SQL Distinct
SQL Order By
SQL Try It
SQL Insert
SQL Update
SQL Delete
SQL Count

SQL Advanced:

SQL Functions
SQL Group By
SQL Aliases
SQL Join
SQL Create
SQL Alter

SQL Quiz Test

Resources:

SQL Books












SQL Group By and Having




Aggregate functions (like SUM) often need an added GROUP BY
functionality.


The GROUP BY Keywords


The GROUP BY keywords have been added to SQL because aggregate functions
(like SUM) return the aggregate of all column values every time they are called.

Without the GROUP BY functionality, finding the sum for each individual group of
column values was not possible.


The syntax for the GROUP BY function is:


SELECT column,SUM(column) FROM table GROUP BY column




GROUP BY Example
This "Sales" Table:


Company
Amount


W3Schools
5500


IBM
4500


W3Schools
7100


And This SQL:

SELECT Company, SUM(Amount) FROM Sales

Returns this result:


Company
SUM(Amount)


W3Schools
17100


IBM
17100


W3Schools
17100


The above code is invalid because the column returned is not part of an
aggregate. A GROUP BY clause will correct, as in this SQL:


SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company

Returns this result:


Company
SUM(Amount)


W3Schools
12600


IBM
4500





The HAVING Keyword


The HAVING keyword has been added to SQL because a WHERE keyword can not be used
against aggregate functions
(like SUM).

Without the HAVING keyword it would not be possible to test for function
result conditions.

The syntax for the HAVING function is:


SELECT column,SUM(column) FROM table
GROUP BY column
HAVING SUM(column) condition value

This "Sales" Table:


Company
Amount


W3Schools
5500


IBM
4500


W3Schools
7100


This SQL:

SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company HAVING SUM(Amount)>10000

Returns this result


Company
SUM(Amount)


W3Schools
12600







Jump to : Top Of Page or HOME.


We Help you for free. Please Help us!

Help us correct errors
Help us with spelling and grammar
Tell us what you think
Link to us from your pages



All information in this Web is for training only. We do not make any warranties of its correctness or
its fitness to be used. The risk of using it remains with the user.
Copyright © 1999-2001 by Refsnes Data. All Rights Reserved.










More Tutorials:


HTML  XHTML
XML  XSL
CSS  DTD
WAP  WML
JavaScript
DHTML  Flash
VBScript  ASP
SQL  AppML






News:

The Future ofProgramming

Web Security

Browser News

Web Standards






References:

HTML 4.01 Ref

XHTML 1.0 Ref

WML 1.1 Ref

CSS Reference

XSLT Elements

ASCII Reference

Entity Reference

HTML Colors

Color Values

Color Names

WAP Pages






Validation:


HTML  XHTML
CSS  DTD
XML  WML







About W3Scripts

Please link to us








Larger Text?








 XML Partners: